I hope this is not too late for inclusion in the LPC2388 version...
Since this ARM controller has a dedicated RTC module on chip, I'd like to suggest placing a CR2032 lithium battery with holder on the piggyback module/new PCB. This is the type used on PC motherboards and generally known to be leak free.
I don't know what it involves in terms of software/FPGA coding, but it would be a nice touch having files with correct time stamps. Always if the Amiga OS is Y2k compliant, anyway.
Edwin